Recently, the technology called OpenFlow is proposed as described in Non-Patent Documents 1 and 2. OpenFlow identifies communications as end-to-end flows and performs path control, failure recovery, load balancing, and optimization on a per-flow basis. An OpenFlow switch, which functions as a forwarding node, has a secure channel for communication with an OpenFlow controller, and operates according to the flow table to which information is added, and whose contents are rewritten, according to an instruction from the OpenFlow controller as necessary. In the flow table, a set of the following three is defined for each flow: a matching rule (FlowKey/Matching key) against which a packet header is matched, an action (Action) that defines processing contents, and flow statistical information (Stats) (see FIG. 30).
FIG. 31 shows an example of the action names and the contents of the actions defined in Non-Patent Document 2. OUTPUT is an action for outputting a packet to a specified port (interface). SET_VLAN_VID to SET_TP_DST are actions for modifying the fields of the packet header.
For example, when a first packet is received, the OpenFlow switch searches the flow table for an entry that has a matching rule (FlowKey) that matches the header information of the received packet. If an entry matching the received packet is found as a result of the search, the OpenFlow switch performs the processing contents, described in the Actions field of the entry, for the received packet. On the other hand, if an entry matching the received packet is not found as a result of the search, the OpenFlow switch forwards the received packet to the OpenFlow controller via the secure channel, requests the OpenFlow controller to determine a packet path based on the transmission source/destination of the received packet, receives a flow entry for the packet path, and updates the flow table.
[Non-Patent Document 1]
    Nick McKeown and seven other authors. “OpenFlow: Enabling Innovation in Campus Networks”, [online], [Searched on Feb. 26, 2010], Internet <URL: http://www.openflowswitch.org//documents/openflow-wp-latest.pdf>[Non-Patent Document 2]    “Openflow Switch Specification” Version 1.0.0. (Wire Protocol 0x01) [Searched on Apr. 1, 2010], Internet <URL: http://www.openflowswitch.org/documents/openflow-spec-v1.0.0.pdf>